DDT biotransformation by a delta-class glutathione S-transferase underlies tolerance in honey bees

Bees are key global pollinators but face long-term exposure to pesticide residues. Although the western honey bee (Apis mellifera) shows tolerance to the persistent organic pollutant DDT, the underlying molecular basis remains unclear. Glutathione S-transferases (GSTs) are important detoxification enzymes in bees, yet direct evidence for their involvement in pesticide metabolism remains limited. In insects, Delta- and Epsilon-class GSTs are typically associated with xenobiotic detoxification. However, the A. mellifera genome encodes only a single Delta-class GST, AmGSTD1, and lacks the Epsilon class, suggesting that AmGSTD1 may play an important role in xenobiotic detoxification in honey bees. Here, we combined genetic, biochemical, and computational analyses to investigate the role of AmGSTD1 in DDT detoxification. Silencing of AmGSTD1 in A. mellifera increased susceptibility to DDT stress, whereas transgenic expression of AmGSTD1 in Drosophila melanogaster conferred increased DDT tolerance. Enzyme kinetics and HPLC analyses demonstrated that recombinant AmGSTD1 protein catalyzed the biotransformation of DDT to DDE, while molecular docking further supported the interaction between AmGSTD1 protein and DDT. AmGSTD1 protein was also associated with alleviation of oxidative stress under DDT exposure. Furthermore, the A170V mutation was identified as an important factor affecting the detoxification activity of the AmGSTD1 protein. Overall, these findings provide functional evidence that AmGSTD1 protein contributes to DDT detoxification through both xenobiotic biotransformation and oxidative stress regulation. This study improves our understanding of the molecular mechanisms underlying pesticide tolerance in honey bees.